To win the 2016 Democratic Party nomination for president, a candidate had to rack up 2,383 delegates. Delegates in 2016 or any other year are won through votes from state primaries or caucuses. Generally, delegates are awarded by percentage in Democratic nominating contests; this is in contrast to some Republican contests, which are winner-take-all. So if one Democratic candidate wins 60 percent of the popular vote in a state that offers 10 delegates, for example, that candidate will win six delegates in that state. This continues state by state, and usually one candidate manages to rack up a clear majority of the delegates before the convention.

Delegates won in primaries and caucuses are considered pledged voters, meant to represent the will of the people who voted for a particular candidate. At the national convention, these delegates are expected to vote for the candidate chosen by the thousands of voters they represent. This is not the case with superdelegates.

In the 2016 Democratic primary, there were about 712 superdelegates, making up around 15 percent of the delegate count for the party [source: CBS News]. These superdelegates are Democratic members of Congress, high-ranking members of the Democratic Party, state governors and former presidents and vice presidents [source: NPR].

Superdelegates are simply "unpledged voters." Their vote represents their own choice, rather than the wishes of the voters, and these unpledged delegates can pledge their votes as they see fit.

Superdelegates have to consider how to use their votes carefully. They may:

Vote in step with how the voters in the majority of states voted

Vote in line with Democratic voters nationwide

Vote in favor of the candidate with the most pledged delegates, even if it is just a slim majority.

A superdelegate can also choose to vote his or her "conscience." This is one way of saying that a superdelegate may not vote the way the majority of voters do, but on the candidate he or she feels is best. "Superdelegates are supposed to vote their conscience and supposed to vote for [the] person they think would make the best candidate and the best president," Howard Wolfson of Hillary Clinton's campaign said in February 2008 [source: Miami Herald]. This is what California Congressman Dennis Cordoza did when he officially switched his pledge from Clinton to Obama the following May, citing her "contentious primary campaign" [source: The New York Times].

Cordoza illustrated another characteristic unique to superdelegates -- they're allowed to switch their pledges from one candidate to another. They can also pledge and switch long before the national convention. Most commonly, a superdelegate rescinds his or her pledge based on his or her constituency. In the 2008 primaries, Georgia Rep. David Scott changed his pledge from Sen. Hillary Clinton to Sen. Barack Obama. Around 80 percent of the Democratic voters in Scott's district voted for Obama, and Scott changed his pledge [source: Ohlemacher].

Superdelegates had an almost immediate effect after their creation in 1982. At the 1984 convention -- thanks to superdelegate votes -- Vice-President Walter Mondale won the nomination over rival Sen. Gary Hart, who had won more states than Mondale (although Mondale won more of the popular vote) [source: The New York Times].

Read about why superdelegates may be a good thing -- or could cripple the democratic process -- on the next page.